FIG. 1 depicts a schematic diagram of generating a new perspective by the depth image based rendering method in the prior art. As shown in the drawing, because the visual point synthesis is an important part of stereoscopic (3D) image generation, it usually uses a plurality of staggered reference cameras 11 and virtual cameras 12 to generate a virtual visual point of the stereoscopic image 10, utilizes the depth image based rendering method to conduct visual point synthesis, and uses the information of color and depth to create the new perspective.
FIG. 2 depicts a schematic diagram of the mapping status of the reference view and the virtual view in prior art. As shown in the drawing, the size of the object 15 in the virtual view v is larger than the size of the object 14 in the reference view r. This characteristic is especially happened in the inclined object 13 or in the synthetic extrapolated image. In this situation, if using the reference view r as the reference and mapping every pixel of the reference view r to the virtual view v, some pixels in the virtual view v will not be mapped by any pixel in the reference view r. In order to fix the flaw, the traditional method uses the median filter in the depth map after mapping to fill the pixel gaps between these pixels, but the median filter will damage the depth edge of the virtual view v.
FIG. 3A and FIG. 3B depict schematic diagrams of mapping the reference view to the virtual view by the forward depth mapping method, respectively, in the prior art. FIG. 4A and FIG. 4B depict depth maps of the virtual view of generating stereoscopic image by the forward depth mapping method, respectively, in the prior art.
As shown in FIG. 3A and FIG. 3B, in the traditional depth mapping method, the forward mapping is used in the left depth map and the right depth map to generate the depth map of the virtual view v. However, due to the limitation of both the horizontal coordinate uv and the vertical coordinate of the pixel 17 of the virtual view v are integer values, the depth map after mapping may generate some pixel gaps between the plurality of the pixels 17. Therefore, the crack 173 of the virtual view v of the stereoscopic image 10 in FIG. 4A and FIG. 4B is generated. In FIG. 3A and FIG. 3B, the depth value of the pixel 16 of the reference view r can be derived from the disparity 161. The depth value of the pixel 17 of the virtual view v can be derived from the disparity 171.
In the first quantitative error of the forward depth mapping method of FIG. 3A, the crack 173 of FIGS. 4A and FIG. 4B will occur in the inclined object. In the second quantitative error of the forward depth mapping method of FIG. 3B, when mapping the pixels 16 of the reference view r to the virtual view v, the disparity 161 (or depth value) of the pixel 16 of the reference view r will be mapped to the pixel gap 172 of the pixel 17 of the virtual view v as the disparity 171 (or depth value), so that the content of the background 18a will appear in the content of the foreground 18b. 
The cause of the above two quantitative errors is that the prior art maps every pixel 16 from the reference view r to the virtual view v. Therefore, after the horizontal coordinates uv, the vertical coordinates and disparities 161 (or depth values) of the pixels 16 of the reference view r being rounded off, the plurality of pixels 16 of the reference view r cannot be all mapped to the plurality of the pixels 17 of the virtual view v, so that the pixel gap 172 and the crack 173 will be generated between the plurality of the pixels 17 of the virtual view v.
Consequently, how to overcome the above problem of prior art, in fact, has become anxious to resolve the issue.